The increase in the popularity of highly portable telecommunications has led to an increase in the number and types of radio communications systems. For example, Personal Communication Systems (PCS), which may comprise second generation cordless telephones (CT-2), utilize digital telephone technology to release a user from the confinement of using his telephone only in his home. In a PCS system, the CT-2 handset can be carried on one's person and calls can be made by establishing a radio frequency link with a telepoint base station or a private base station. Other recently developed, highly portable radio communications systems are the Digital European Cordless Telephone system (DECT), the Bellcore FA technology, and a telecommunications system developed by Qualcomm.
Yet, not all radio frequency (RF) communications systems are homogeneous requiring an allocation of RF bandwidth for the various RF communication systems. In the United States, the Federal Communications Commission (FCC) governs the allocations of various radio frequency bands for use by the multiplicity of heterogeneous RF communication systems. The rules and regulations of the FCC require that radio frequency operation within an allocated frequency band be licensed by the FCC.
Virtually no frequencies below 3 GHz in the RF spectrum in the United States are unallocated. Currently no frequency bands are allocated for usage by the new highly portable RF communication systems, such as PCS. To obtain reallocation of a frequency band from the FCC could take a long time and require a substantial investment of time and funds for political lobbying and other bureaucratic requirements.
Certain frequency bands under FCC Part 15 Regulations are allocated for unlicensed operation. The newly developed RF communication systems could operate in these unlicensed frequency bands. However, there could be an unlimited number of different RF communication systems within a frequency band and the possible users could be broadcasting in any of a number of different multiple access techniques, such as time division multiple access (TDMA), frequency division multiple access (FDMA), code division multiple access (CDMA) or wireless data systems using carrier sense multiple access (CSMA). Even systems sharing the same multiple access technique may have different parameters, protocols and Common Air Interfaces (e.g., the frame length and the number of time slots in a frame of a TDMA system). The transmitters may be isochronous and transmit at regular intervals (as likely with voice service), or asynchronous and transmit at irregular intervals (e.g., local area network (LAN) data systems).
It has been proposed that unlicensed PCS systems operate within a 20 MHz bandwidth in the 2 GHz band. A service provider who provides a PCS system utilizing unlicensed RF operation, however, cannot predict the future use of the RF channels adopted. Many communication service providers are reluctant to invest much money in RF communication system infrastructure which would operate in an unlicensed spectrum because of the risk that the spectrum could become overcrowded, chaotic, and ultimately unusable for public telepoint service.
Thus, what is needed is a method and apparatus to allow devices of different RF communication systems to coexist in an interference-limited environment by constraining all devices to a known behavioral envelope.